SAN JOSE, Calif. – No titles changed hands in Strikeforce’s first championship doubleheader of 2011.

In the organization’s first major show of the year, Strikeforce welterweight champion survived very live underdog Evangelista “Cyborg” Santos and ultimately scored a second-round submission victory.

The bout headlined Saturday’s “Strikeforce: Cyborg vs. Santos” event at the HP Pavilion in San Jose, Calif. The event aired on Showtime.

Although scheduled for five rounds, Santos clearly had no intention of going the distance. And though criticized as an unworthy title challenger, the former PRIDE fighter tripped up Diaz early.

But after chopping away with leg kicks and proving the durability of Diaz’s chin with some heavy blows, Santos simply ate punch after punch as his defenses faded away. Santos likely gained some confidence from the low kicks that bettered Diaz’s right knee. But Diaz closed out the round with his usual quick fire of punches, few of which Santos defended. A big left hand in the final seconds likely won the champ the round.

The slugfest continued in the second round, and each fighter’s chin was tested. Santos finally went on the defensive when Diaz sneaked through a few effective elbow-strike crosses. But Santos regrouped and found success with a few well-places counter-shots. But then came what would prove to be a mistake.

Santos scored the ill-advised trip-takedown late in the round. Diaz quickly saw an opening for an armbar, and though he initially defended by rolling out of the pressure, Santos was forced to tap out from the submission with just 10 seconds remaining in the fight.

Diaz admittedly got a challenge in his second successful title defense.

“I figured I’d put on pressure so he’d have to do something to avoid more punches,” the jiu-jitsu based Diaz said while explaining why Santos went for the takedown.

While known for a brash attitude and plenty of trash-talking, Diaz was all compliments when it came to Santos.

“I respect the way he fights,” Diaz said. “He doesn’t mess around. He came out here and fought me. He didn’t play games.”

Diaz (24-7 MMA, 5-0 SF) now has won nine straight fights, eight via stoppage, and Strikeforce’s thin welterweight division offers few high-profile candidates outside of Paul Daley for a next title challenge.

Santos (18-14 MMA, 1-2 SF) sees a two-fight win streak come to an end while suffering his fifth loss in eight fights.

Souza uses ground assault to defend title

Strikeforce middleweight champion Ronaldo “Jacare” Souza has his first title defense in the books, though challenger Robbie Lawler may be kicking himself for a lost opportunity.

Lawler had his opening in the first round when Souza got into a slugfest with the striker. Souza was stunned and then floored when Lawler unloaded a lunging knee and quick left hook. But the challenger inexplicably followed Souza to the mat, where the champ was able to regain his wits while awaiting the round’s end.

Souza then put on a ground clinic in the second round. After getting the takedown, Souza rotated between dominant positions with heavy ground and pound and multiple near-successful submission attempts. Lawler took substantial damage in the round but escaped an armbar attempt to survive it. Still, MMAjunkie.com scores it 10-8 for the champ due to the sheer dominance.

Souza again took the fight to the mat in what would prove to be the decisive third round. Lawler did little to defend, and Souza quickly moved to his back and secured his hooks. While initially fending it off, Lawler eventually succumbed to the rear-naked choke when Souza torqued it at the 2:00 mark of the round.

“I came prepared for everything,” said Souza, who won the belt, which was vacated by Jake Shields, with an August win over Tim Kennedy. “I have great coaches, friends and training partners. I feel great now.”

Souza (14-2 MMA, 4-0 SF) now has won his past four fights, all in Strikeforce. Lawler (20-7 MMA, 2-3 SF), meanwhile, has rotated between wins and losses for the fifth time under the Strikeforce banner.

NFL vet Walker makes quick work of Carson

Don’t piss off Herschel Walker.

That’s the lesson Scott Carson will take away from his heavyweight bout with the former NFL great. After grazing Walker with a head kick in the opening seconds of their fight, Carson would offer little the rest of the way and ultimately suffered a first-round TKO loss.

After taking the kick, Walker yelled, likely more in frustration than anger. But either way, Carson paid the price. Walker dropped him with a quick right hand, avoided a leg lock, and then blasted away on the one-time WEC fighter with countless blows as he turtled up on the mat. Tired of the abuse, Carson attempted to get back to his feet, but he quickly was put back on the canvas with Walker straight right.

The ref had seen enough and halted the bout at the 3:13 mark of the opening round.

“I took a kick when I think I was getting a little too excited,” Walker said. “When you’re in an MMA fight, you shouldn’t take a kick like that.”

Walker said his and American Kickboxing Academy trainer Javier Mendez’s plan was to launch a quick assault.

“One thing Javier told me is to be on offense,” he said. “That’s what I’ve been saying. I’ve got to be on offense … and control what I’m doing in the cage.”

Walker (2-0 MMA, 1-0 SF), who was forced out of a December fight with Carson after suffering a facial cut in training, saw 12 months between his first two pro bouts. But the soon-to-be 49-year-old said he plans to fight more frequently this year.

Roger Gracie continue his winning ways and picked up arguably the biggest victory of his MMA career with a first-round submission victory over veteran light heavyweight Trevor Prangley.

After a few uneventful minutes with limited standup from both competitors, Gracie got the takedown he needed. Prangley remained in a seated position against the cage, but Gracie methodically flattened him out, took his back, and secured a vise-like body lock before securing the fight-ending rear-naked choke.

The end, which Prangley frantically tried to fight off, came at the 4:19 mark of the round.

“I think everything happened as planned,” Gracie said. “I knew he was heavy-handed, but I know I have the reach on my feet. So I played with the jab, and I knew he was going to come in hard. That was my plan to shoot in, and it happened exactly like that.”

Gracie (4-0 MMA, 2-0 SF), who registered just three pro MMA bouts in his first four years while mixing in numerous grappling tournaments, plans to amp up the frequency of his MMA fights in 2011. Prangley (23-7-1 MMA, 3-2-1 SF) falls to 1-2-1 in his past four fights.

Hill, Kesler score upsets in prelims

Nate Moore (7-2 MMA, 2-1 SF) used a quick start to the second round to set up a knockout victory over fellow welterweight Nathan Coy (8-4 MMA, 1-2 SF) in the night’s featured preliminary-card bout. The fighters, who originally were slated to fight earlier this month before the bout was delayed a few weeks, jockeyed for position on the mat through the first round. But once standing in the second, Moore connected on a brutal right that was followed by a quick left. Coy, who was sent to the mat, was forced to cover up from the blows just 25 seconds into the round.

In a shocking upset, Isaiah Hill (5-7-1 MMA, 1-2 SF) used two devastating knees and snapped a six-fight winless streak to score a first-round submission victory over lightweight Bobby Stack (8-2 MMA, 3-2 SF). After some flashy kicks fell short, Hill countered Stack’s takedown attempt with a grazing knee to the head. With his opponent wobbly, Hill followed with another flying knee that popped Stack, set up a takedown and resulted in a fight-ending triangle choke just 62 seconds into the fight.

In a 180-pound catchweight fight, Ron Keslar (5-3 MMA, 2-0 SF) scored an upset and snapped his opponent’s five-fight win streak by stopping Eric Lawson (9-3 MMA, 5-1 SF) with a first-round submission victory. Lawson attempted to get the fight to the mat, but Keslar wrestled him for dominant position. Although he fended off a triangle choke, Lawson immediately was forced to tap out from the following armbar at the 1:57 mark.

Former undefeated kickboxer Germaine de Randamie (2-1 MMA, 1-0 SF) used a decent enough ground game to avoid trouble and set up her heavy blows en route to a first-round TKO victory over Stephanie Webber (1-2 MMA, 0-1 SF). After surviving her opponent’s submission attempts, De Randamie got back to her feet, secured the clinch and knocked out her opponent with a vicious knee to the face at the 4:25 mark of the opening round.

James Terry (9-2 MMA, 4-1 SF) quietly picked up his fourth win in five Strikeforce fights with an impressive striking display against fellow welterweight Lucas Gamaza (4-2 MMA, 0-1 SF). Terry unloaded a steady stream of blows that eventually forced Gamaza to the mat to cover up. The end came at the 3:26 mark of the opening round.

In the night’s opening bout, Jenna Castillo (1-0 MMA, 0-1 SF) made a successful pro debut, displayed impressive striking skills and suitable ground defense, and ultimately scored a second-round TKO of Charlene Gellner (0-1 MMA, 0-1 SF). Castillo, who dominated the action standing, used a right cross that was followed with a knee to the head to set up the stoppage at the 3:57 mark of the round.